1. Field of the Invention
The present invention relates to an electric double layer capacitor (EDLC), and more particularly, to an EDLC which has high energy density and ultra low equivalent series resistance (ESR) characteristics, while having a chip structure in which the thickness is easily controlled, and a method of manufacturing the same.
2. Description of the Related Art
In various electronic products such as information communication devices, a stable energy supply is considered to be an important element. In general, such a function is performed by a capacitor. That is, the capacitor serves to store electricity in a circuit provided in various electronic products such as information communication devices and then discharge the electricity, thereby stabilizing the flow of electricity in the circuit.
A general capacitor has a short charge and discharge time, a long lifespan, and high output density. However, since the general capacitor has low energy density, there is a limitation in using the capacitor as a storage device. To overcome such a limitation, a new category of capacitors such as an EDLC have been recently developed, which have a short charge and discharge time and high output density. Much attention is being paid to such capacitors as a next generation energy device together with secondary cells.
The EDLC is an energy storage device using a pair of charge layers (electrode layers) having a different polarity. The EDLC may perform continuous electric charge and discharge and has higher energy efficiency and output and greater durability and stability than general other more general capacitors.
A basic structure of the EDLC includes a polarizable electrode, an electrolyte, and a separator. The polarizable electrode has an active material layer and a current collection body, the active material layer having a relatively large surface area like a porous electrode. The operational principle of the EDLC is an electro-chemical mechanism in which electricity is generated when a voltage of several volts is applied to both ends of a unit cell electrode such that ions in the electrolyte move along an electric field to be adsorbed by electrode surface.
EDLCs which are currently commonly used may be roughly classified into two types, that is, a wound structure and a coin-shaped structure.
The wound-structure EDLC is manufactured by winding a current collection body and an insulating paper serving as a separator together in a circular shape, the current collection body being coated with an active material layer such as activated carbon. The coin-shaped EDLC is manufactured by punching an activated carbon electrode and an insulating paper to insert into a coin-shaped metal case.
Such structures according to the related art should implement high energy density and low ESR. That is, a large area is required in order to obtain high energy density. However, a process of implementing the large area is complicated, and separate external terminals are connected to collect currents into unit cells. Therefore, resistance inevitably increases, making it difficult to implement low ESR characteristics.